<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title></title>
</head>
<body>
<script type="text/javascript">
	let arr = [1, 4, 5, 7]
	//数组[数组.length] = "" 恒定往数组最后添加一个数据
	arr[5] = 'hi'
	console.log(arr)

	//数组的取赋值
	console.log(arr[2]) //5
	arr[2] = "hello"
	console.log(arr)
</script>
</body>
</html>